Method of forming a three-dimensional body

ABSTRACT

A method of forming a three-dimensional body from a mixture, wherein the mixture can comprise dispersed solid polymeric particles and a curable binder. In a particular embodiment the solid polymeric particles can be fluoropolymeric particles. The method can include at least partial removal of the cured binder and sintering, to obtain a sintered polymeric three-dimensional body. In one embodiment, the sintered three-dimensional body can be PTFE.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. § 119(e) to U.S.Provisional Application No. 62/535,521, entitled “METHOD OF FORMING ATHREE-DIMENSIONAL BODY,” by Jean-Marie Lebrun et al., filed Jul. 21,2017, which is assigned to the current assignee hereof and isincorporated herein by reference in its entirety.

FIELD OF THE DISCLOSURE

The present disclosure relates to a method of forming athree-dimensional body from a mixture comprising dispersed solidpolymeric particles, and particularly the forming of a three-dimensionalbody from a mixture comprising solid fluoropolymeric particles.

BACKGROUND

The manufacturing of polymeric three-dimensional bodies based on a layerby layer built up of a radiation curable liquid material has become ofincreasing interest, especially in view of the enhancement in productionspeed if a bottom-up technique is employed. One disadvantage ofthree-dimensional printing is the limited spectrum of curable resinsthat can be used and the limited material type of formed polymericbodies. It is desirable to expand the scope of polymer materials thatmay be formed during 3D printing to a broader spectrum of polymers, suchas particularly fluoropolymers, for example, polytetrafluoroethylene(PTFE).

SUMMARY

According to one embodiment, a method of forming a three-dimensionalbody, comprising: providing a mixture comprising a curable binder anddispersed solid polymeric particles; and forming a three-dimensionalbody from the mixture by curing the binder, wherein forming includestranslation and growth of the three-dimensional body from an interfaceof the mixture, and the solid polymeric particles have a higher thermaltransition temperature than the decomposition temperature of the curedbinder.

According to another embodiment, a method of forming a three-dimensionalbody comprises providing a mixture comprising a curable binder anddispersed solid particles, the solid particles including afluoropolymer; and forming a three-dimensional body from the mixture bycuring the binder, wherein forming includes translation and growth ofthe three-dimensional body from an interface of the mixture.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure may be better understood, and its numerousfeatures and advantages made apparent to those skilled in the art byreferencing the accompanying drawings.

FIG. 1 includes a scheme of the process of forming a sinteredthree-dimensional polymeric body according to one embodiment.

FIG. 2A includes an illustration of an assembly according to oneembodiment, showing the starting phase of forming of a three-dimensionalbody.

FIG. 2B includes an illustration of an assembly according to oneembodiment, showing a later phase of forming of a three-dimensionalbody.

FIG. 3 includes a graph illustrating a viscosity profile of a mixturecomprising dispersed solid PTFE particles according to one embodiment.

FIG. 4 includes an image illustrating the shrinkage of a formedthree-dimensional body after drying and sintering according to oneembodiment.

FIGS. 5A, 5B, and 5C include images of formed PTFE comprising bodiesbefore sintering in the presence of a dye according to embodiments.

FIG. 6 includes images of formed PTFE comprising body after forming andafter drying and sintering according to one embodiment

FIG. 7A includes an image of a formed FEP comprising body after drying,which was formed without the presence of a dye.

FIG. 7B includes an image of a formed FEP comprising body after drying,which was formed in the presence of a dye according to one embodiment.

FIGS. 8A, 8B, and 8C include images of formed FEP comprising bodiesbefore and after sintering (300° C.) according to embodiments.

FIG. 9 includes a graph illustrating a thermogravimetric analysis (TGA)of a FEP comprising three-dimensional body according to one embodiment.

FIG. 10 includes a graph illustrating a differential scanningcalorimetry (DSC) measurement for solid PTFE particles used as startingmaterial for the forming of a three-dimensional body according to oneembodiment.

FIG. 11A includes a drawing illustrating a side view of a 3D model forprinting.

FIG. 11B includes a drawing illustrating a three dimensional view of a3D model for printing.

FIGS. 12A, 12B, and 12C include side view images of PTFE comprisingbodies after drying, wherein the bodies were formed with varying amountsof Rhodamine B in the mixture according to embodiments.

FIG. 13A includes a top view of an image of a PTFE comprising body afterdrying (also shown as side view in FIG. 12B) with markings of positionsof thickness measurements of the formed walls according to oneembodiment.

FIG. 13B includes a top view of an image of a PTFE comprising body afterdrying (also shown as side view in FIG. 12B) with markings of positionsof gap size measurements between the walls according to one embodiment.

FIG. 14A includes a top view of an image of a sintered PTFE comprisingbody according to one embodiment.

FIG. 14 B includes a side view of an image of a sintered PTFE comprisingbody according to one embodiment.

FIG. 14C includes a top view of an image of a sintered PTFE comprisingbody with markings of positions of thickness measurements of the wallsaccording to one embodiment.

FIG. 14D includes a top view of an image of a sintered PTFE comprisingbody with markings of positions of gap size measurements between thewalls according to one embodiment.

FIG. 15 includes images of a sintered PTFE comprising body before andafter mechanical testing of the elongation at break according to oneembodiment.

DETAILED DESCRIPTION

As used herein, the terms “comprises,” “comprising,” “includes,”“including,” “has,” “having” or any other variation thereof, areintended to cover a non-exclusive inclusion. For example, a process,method, article, or apparatus that comprises a list of features is notnecessarily limited only to those features but may include otherfeatures not expressly listed or inherent to such process, method,article, or apparatus.

As used herein, and unless expressly stated to the contrary, “or” refersto an inclusive-or and not to an exclusive-or. For example, a conditionA or B is satisfied by any one of the following: A is true (or present)and B is false (or not present), A is false (or not present) and B istrue (or present), and both A and B are true (or present).

Also, the use of “a” or “an” are employed to describe elements andcomponents described herein. This is done merely for convenience and togive a general sense of the scope of the invention. This descriptionshould be read to include one or at least one and the singular alsoincludes the plural unless it is obvious that it is meant otherwise.

As used herein, the term mixture refers to a fluid of a certainviscosity, including a liquid component and solid particles. The liquidcomponent may include a curable binder and a solvent.

As used herein, the term solid polymeric particles refers to polymericparticles that remain solid in the mixture and do not dissolve in theliquid component of the mixture during forming of the three-dimensionalbody. In a particular embodiment, the solid polymeric particles includea fluoropolymer.

Various embodiments of the present disclosure will now be described, byway of example only, with reference to the accompanying drawings.

The present disclosure relates to a method of forming athree-dimensional body from an interface of a mixture includingdispersed solid polymeric particles and a curable binder. The method caninclude removal of at least a portion of the cured binder from theformed body wherein the shape of the body can be maintained.

According to one embodiment, the method may include the followingsteps: 1) providing a mixture comprising dispersed solid polymericparticles and a curable binder; 2) forming a three-dimensional body froman interface of the mixture; 3) drying the formed three-dimensional bodyat elevated temperatures to remove solvent present in the formed body;4) removing at least a portion of the cured binder by heating thethree-dimensional body to a decomposition temperature of the binder; and5) sintering the three-dimensional body close to a thermal transitiontemperature of the solid polymeric particles to form a sinteredthree-dimensional body. A simplified scheme of the process isillustrated in FIG. 1.

In one embodiment, the mixture can be prepared by using a dispersion ofsolid polymeric particles in a solvent, and mixing the dispersiontogether with the curable binder. In one aspect, the binder may be atleast partially soluble in the solvent.

The forming of the three-dimensional body can be conducted in anassembly, as illustrated in FIG. 2A. The assembly can have a computercontrolled electromagnetic radiation unit (11), a chamber (12), and aconstruction unit (13). The electromagnetic radiation unit (11) can beconfigured to deliver electromagnetic radiation to a portion of themixture, wherein the electromagnetic radiation can have a particularwavelength, including for example an ultraviolet radiation (UV) orvisible light. The assembly can include a radiation source (14), forexample, a laser or a light emitting diode (LED), which can beconfigured to project a varying computer-aided design/computer-aidedmanufacturing (CAD/CAM) created two-dimensional image onto a transparentwindow (15) at the bottom of the chamber (12). The chamber (12) caninclude a mixture (16) that can include a radiation curable material andsolid particles. The transparent window (15) of the chamber (12) can besemipermeable for a particular inhibitor, which may be a gaseousmaterial. In such instances, the semipermeable layer is selectivelypermeable, such that it is configured to allow for the transfer of theinhibitor into the mixture, but may not allow transfer of othermaterials (e.g., water) through the transparent window (15). Thetransparent window (15) may include an additional semipermeable layer(not shown) for the penetration of an inhibitor, for example air oroxygen, into the mixture (16) of the chamber (12). During the formingprocess, the inhibitor may enter the chamber (12) by permeating thetransparent window (15) and form an inhibition zone (17) at a bottomregion of the mixture (16). In the inhibition zone (17) the inhibitorcan limit or prevent curing of the mixture (16) by the electromagneticradiation.

According to one embodiment, a carrier plate (18) can be positionedabove the chamber (12). The position between the carrier plate (18) andthe mixture in the chamber (12) can be changed during the formingprocess to facilitate formation of the three-dimensional body. When theformation of the three-dimensional body is started, the carrier plate(18) can be emerged into the mixture (16) up to a pre-calculateddistance from the interface of the inhibition zone (22). According toone embodiment, the pre-calculated distance corresponds to a portion ofthe mixture that can be radiation cured (translated from liquid to solidstate) if subjected to electromagnetic radiation from the radiation unit(11) underneath the chamber (12), and is further on called “translatingportion” (19). The radiation cured translating portion (19) can beadhered to the carrier plate (18) and can be vertically moved away fromthe interface of the inhibition zone (22). Concurrently with the upwardsmovements of the carrier plate (18) and the attached solidifiedtranslating portion (19), mixture (16) from the sides of thepolymerization chamber or from a reservoir (20) can fill the releasedspace. The construction is designed to move the carrier plate (18)continuously upwards in vertical direction (i.e., Z-direction) at aspeed that corresponds to the time needed for radiation curing mixture(16) that replaces the upwards moved solidified translating portion.

FIG. 2B includes an illustration of a partially formed three-dimensionalbody according to an embodiment. The partially formed body includesthree solidified and unified translating portions (21) and onetranslating portion (19) which is subjected to radiation curing.

The increase in distance between the carrier plate (18) and the mixture(16) when forming the three-dimensional body can be caused by movingeither the carrier plate (18) or the chamber (12) or both carrier plate(18) and chamber (12) in relation to each other.

The carrier plate (18) of the assembly may be configured for continuousmovement to facilitate formation of the three-dimensional body as thecarrier plate (18) is moved.

The inhibition zone (17) is a zone of the mixture, which is onlydistinguished from the other part of the mixture by the presence of aninhibitor in a concentration that the mixture may not cure if exposed toelectromagnetic radiation. Actual solidification and forming of thethree-dimensional body starts at the interface of the inhibition zone(22). The interface of the inhibition zone (22) can also be consideredas an interface of the mixture from where the forming of thethree-dimensional body starts.

In order to assure curing of the mixture throughout a thickness of thetranslating portion (19), the cure depth (23) can be controlled that itreaches a larger distance through the mixture in Z-direction from thetransparent window (15) than the thickness of the translating portion(19). In one embodiment, the cure depth (23) may reach at least 25%further than the thickness of the translating portion (19), such as atleast 30%, at least 35%, or at least 40%.

In one embodiment, the thickness of the translating portion (19) can beat least 1 μm, such as at least 3 μm, at least 5 μm, such as at least 10μm, at least 15 μm, at least 20 μm, at least 30 μm, or at least 50 μm.In another embodiment, the thickness of the translating portion may benot greater than 700 μm, such as not greater than 600 μm, not greaterthan 500 μm, not greater than 450 μm, or not greater than 400 μm.Thickness of the translating portion can be a value between any of themaximum and minimum values note above, such as from 1 μm to 700 μm, from10 μm to 650 μm, from 50 μm to 350 μm, or from 5 μm to 50 μm.

The formation of the three-dimensional body may not necessarily beconsidered a layer-by-layer forming process. Instead, the formingprocess (e.g., curing) may be in the form of a gradient ofsolidification (e.g., polymerization).

As used in the context of the present disclosure, continuous translationand growth of the three-dimensional body means that the carrier plate(18) can be moved in a continuous manner or in discrete steps with shortstops between each step. In certain instances, the continuoustranslation and growth will be characterized by a gradient ofsolidification that is maintained while forming the three-dimensionalbody. A gradient of solidification means that a continuouspolymerization reaction is maintained across the thickness of thetranslating portion (19), with the lowest degree of solidification nextto the interface of the inhibition zone (22) and the greatest degree ofsolidification at the opposite end across the thickness of thetranslating portion (19). The three-dimensional body formed by theprocess of continuous translation can thereby possess a non-layeredinternal structure, such that in a crosscut along the z-axis, changes inthe morphology of the three-dimensional body are not visible to thenaked eye.

In those embodiments utilizing short stops in the movement of thecarrier plate (18), such stops are generally brief and suitable formaintaining the above-described gradient of solidification. According toone embodiment, the stops can be for a duration of at least 1microsecond, such as at least 300 microseconds, at least 500microseconds, at least 800 microseconds or even at least 1000microseconds. In other embodiments, the stops may be for a duration ofnot longer that 1 second, such as not longer than 0.5 seconds, notlonger than 0.3 seconds or not longer than 0.2 seconds or even notlonger than 0.1 seconds. It will be appreciated that the stops can havea duration within a range including any of the minimum and maximumvalues note above, such as from 1 microsecond to 1 second or from 300microseconds to 0.5 seconds or from 1000 microseconds to 0.1 seconds.

In further embodiments, the method of the present disclosure can alsoinclude longer stops during the forming of the three-dimensional body,such that the gradient of solidification may be interrupted and thetranslation is not continuous as defined above. Such longer stops may bedesired for the making of a body having defined regions which arecleavable.

The inhibition zone (17) can be a part of the mixture and located nextto the transparent window (15) of the chamber, where the mixture doesnot cure or only to a very limited extend under electromagneticradiation. Accordingly, the inhibition zone (17) may facilitate limitedor no adhesion of the radiation cured material to the bottom of thechamber (12), which may facilitate simpler release of the body from thechamber after forming is completed.

The inhibition zone (17) can be formed when the inhibitor enters thechamber (12) through the transparent and semipermeable window (15), andmay be regulated in its thickness by the concentration of the inhibitor.

In one embodiment, the thickness of the inhibition zone (17) can bevaried by varying the intensity of the applied electromagneticradiation.

In another embodiment, the thickness of the inhibition zone (17) can bevaried by varying the pressure of a gaseous inhibitor for forming theinhibition zone.

In one embodiment, the thickness of the inhibition zone may be at least0.5 μm, such as at least 1.0 μm, at least 2.0 μm, or at least 5 μm. Inanother embodiment, the inhibition zone may not be greater than 600 μm,such as not greater than 500 μm, not greater than 300 μm, or not greaterthan 100 μm. It will be appreciated that the thickness of the inhibitionzone can be a value between any of the maximum and minimum values notedabove, such as from 0.5 μm to 600 μm, from 1.0 μm to 450 μm, or from 3μm to 200 μm.

The inhibitor may preferably be an oxygen containing gas, such as air,mixtures of an inert gas and oxygen, or pure oxygen. In another aspect,when oxygen cannot inhibit the activity of the photoinitiator (forexample, when a cationic photoinitiator is used) the inhibitor can be anamine, e.g., ammonia, ethyl amine, di and trialkyl amines, carbondioxide, or combinations thereof.

In one embodiment, the inhibitor can be pure oxygen, and the oxygen maypenetrate the semipermeable layer in an amount of at least 0.1 Barrer,such as at least 1 Barrer, at least 5 Barrer, at least 10 Barrer, or atleast 30 Barrer.

Although the term “inhibition zone” appears to indicate that nopolymerization reaction may take place in that area of the mixture, itwill be appreciated that polymerization reactions can also occur to alimited extent in the inhibition zone (17). The inhibition zone (17) maybe also described as a gradient of polymerization, where with increasingdistance from the bottom surface of the chamber larger amounts ofpolymerization reactions can happen, but these polymerization reactionsmay not completely cure the mixture, and the mixture is still maintainedin a liquid stage. The interface of the inhibition zone (22) may beunderstood as the area of the inhibition zone (17) where thepolymerization reactions start to form a solid material.

Varying the thickness of the translating portion (19) can includeadjusting the position of the carrier plate (18) onto which thethree-dimensional body is attached relative to the interface of theinhibition zone (22).

The binder of the mixture can be a radiation curable binder. Duringforming of the body, the mixture can be subjected to electromagneticradiation having a wavelength in a range from 200 nm to 760 nm andthereby curing the radiated binder. In a preferred aspect, the range ofthe electromagnetic radiation may be from 370 nm to 450 nm, or from 380nm to 410 nm.

In embodiments, the electromagnetic radiation can be created by a laser,a light emitting diode (led), or by electron beam radiation.

In one embodiment, the electromagnetic radiation applied for curing thebinder can have an energy of at least 1 mJ/cm², such as at least 5mJ/cm², at least 10 mJ/cm², at least 20 mJ/cm², at least 30 mJ/cm², atleast 50 mJ/cm² or at least 80 mJ/cm². In another embodiment, theelectromagnetic radiation can have an energy not greater than 450mJ/cm², such as not greater than 400 mJ/cm², not greater than 350mJ/cm², not greater than 300 mJ/cm², not greater than 250 mJ/cm², notgreater than 200 mJ/cm², or not greater than 100 mJ/cm². It will beappreciated that the electromagnetic radiation energy can be a valuebetween any of the maximum and minimum values noted above, such as from1 mJ/cm² to 450 mJ/cm², from 50 mJ/cm² to 300 mJ/cm², from 40 mJ/cm² to200 mJ/cm², or from 20 mL/cm² to 100 mJ/cm².

In a particular embodiment, the method of the present disclosure maycure the binder in the translating portion (19) during continuousforming of the three dimensional body at a UV power of at least 0.1mW/cm², such as at least 0.5 mW/cm², at least 1.0 mW/cm², or at least3.0 mW/cm². In another particular embodiment, the applied UV powerduring forming may be not greater than 250 mW/cm², such as not greaterthan 150 mW/cm², not greater than 100 mW/cm², not greater than 50mW/cm², not greater than 30 mW/cm², not greater than 20 mW/cm², notgreater than 13.0 mW/cm², not greater than 12 mW/cm², or not greaterthan 10 mW/cm². It will be appreciated that the applied UV power can bea value between any of the maximum and minimum values noted above, suchas from 0.1 mW/cm² to 250.0 mW/cm², from 1.0 mW/cm² to 100 mW/cm² orfrom 2.0 mW/cm² to 10 mW/cm².

The electromagnetic radiation (14) can cure the binder in the mixture(16) up to a certain distance throughout the mixture, hereinafter calledthe cure depth (23). The cure depth (23) may be affected by the size,type, and concentration of the solid polymeric particles and therefractive index of the particle slurry.

The method of the present disclosure can continuously manufacture athree-dimensional body at a high production speed. In one aspect, thecreating of the three-dimensional body can be completed at a speed rateof at least 1 mm/hour, such as at least 5 mm/hour, at least 10 mm/hour,at least 20 mm/hour, at least 25 mm/hour, at least 40 mm/hour, at least50 mm/hour, or at least 60 mm/hour. In another aspect, the forming speedmay be not greater than 5000 mm/hour, such as not greater than 3000mm/hour, not greater than 1000 mm/hour, not greater than 500 mm/hour, ornot greater than 100 mm/hour. The forming speed can be a value betweenany of the maximum and minimum values noted above, such as from 1mm/hour to 5000 mm/hour, from 5 mm/hour to 500 mm/hour, or from 10mm/hour to 80 mm/hour.

The solid particles can be polymeric solid particles having a thermaltransition temperature which is higher than the decompositiontemperature of the cured binder. This can allow at least a partialremoval of the cured polymeric binder by maintaining the shape of thethree-dimensional body, wherein the solid polymeric particles form apercolated network. As used herein, the thermal transition temperatureof the solid polymeric particles relates to the temperature at which thepolymeric particles start melting or start to undergo a glass transitionlike stage. The thermal transition temperature can be determined byDifferential Scanning calorimetry (DSC) or Differential Thermal Analysis(DTA). FIG. 10 illustrates an example of a DSC measurement for solidPTFE particles, showing an onset (i.e., start) of the melting point ofthe PTFE particles at 329° C. Furthermore, as used herein, thedecomposition temperature of the binder relates to the temperature atwhich 5 wt % of the binder based on the total weight of the binder isdecomposed into volatile compounds and removed from the body. Thedecomposition temperature of a binder can be determined, for example,from a Thermal Graphimetric Analysis (TGA) graph, as illustrated in FIG.9, and further explained in the examples.

In a certain embodiment, the solid polymeric particles can befluoropolymers. Non-limiting examples of fluoropolymers can bepolytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene(FEP), perfluoroalkoxyethylene (PFA), ethylene-tetrafluoroethylene(ETFE), polyvinylidone fluoride (PVDF), ethylene-chlorotrifluoroethylene(ECTFE), perfluoromethyl vinyl ether (MFA), or any combination thereof.In a particular embodiment, the material of the solid particles can bePTFE. In another particular embodiment, the material of the solidparticles can be PFA. In yet a further particular embodiment, thematerial of the solid particles can be FEP.

The solid particles of the present disclosure may not be limited tofluoropolymers. Other suitable solid polymeric particles can bethermoplastics or thermosets having a high thermal transitiontemperature, for example, polyimide (PI), polyetheretherketone (PEEK),polyamide-imide (PAI), poly(etherketon-etherketonketon) (PEKEKK), orpolyethylene imine (PEI).

In embodiments, the polymeric solid particles can have a thermaltransition temperature of at least 240° C., such as at least 250° C., atleast 260° C., at least 300° C., at least 310° C., or at least 320° C.In other embodiments, the thermal transition temperature of the solidparticles may be not greater than 380° C., such as not greater than 360°C., not greater than 340° C., or not greater than 330° C. The thermaltransition temperature of the solid particles can be a value between anyof the maximum and minimum values noted above, such as from 240° C. to360° C., from 260° to 340° C., or from 280° C. to 330° C.

The solid particles contained in the mixture can have an average primaryparticle size of at least 0.06 μm, such as at least 0.070 μm, at least0.080 μm, at least 0.1 μm, at least 0.150 μm, at least 0.2 μm, at least0.23 μm, or at least 0.260 μm. In another aspect, the solid particlescan have an average primary particle size of not greater than 10 μm,such as not greater than 8 μm, not greater than 5 μm, or not greaterthan 1 μm. The average primary size of the solid particles can be avalue between any of the minimum and maximum values noted above, such asfrom 0.06 μm to 1 μm, from 0.07 μm to 5 μm, or from 0.1 μm to 5 μm. Asused herein, the average primary particle size of the solid polymericparticles relates to the average particles size in single form, notincluding particle agglomerates.

In a certain embodiment, the solid polymeric particles dispersed in themixture can form solid polymeric particle aggregates. In one aspect, thesolid particles aggregates can have an average particle size of notgreater than 50 μm, such as not greater than 35 μm, not greater than 20μm, or not greater than 15 μm.

In a further embodiment, the solid polymeric particles can have amolecular weight of at least 1×10⁵ g/mol, such as at least 5×10⁵ g/mol,at least 1×10⁶ g/mol, at least 5×10⁶ g/mol, or at least 1×10⁷ g/mol. Inanother embodiment, the molecular weight of the solid polymericparticles may be not greater than 9×10⁷ g/mol, such as not greater than6×10⁷ g/mol, or not greater than 3×10⁷ g/mol. The molecular weight ofthe solid polymeric particles can be a value between any of the maximumand minimum values noted above, such as from 1×10⁵ g/mol to than 9×10⁷g/mol, from 1×10⁶ g/mol to 6×10⁷ g/mol, or from 1×10⁷ g/mol to 9×10⁷g/mol.

In yet a further embodiment, the solid polymeric particles in themixture, before forming of a three-dimensional body and sintering of thebody, can have a crystallinity of at least 65%, such as at least 70%, atleast 80%, or at least 90%.

A solid polymeric particle, as used herein, maintains solid in themixture during preparing of the mixture and forming of thethree-dimensional body and can include at least 30 wt % of polymersbased on the total weight of the particle, such as at least 40 wt %, atleast 50 wt %, at least 60 wt %, at least 70 wt %, at least 80 wt %, atleast 90 wt %, at least 95 wt %, or at least 99 wt % polymer based onthe total weight of the solid particle. Other components in the solidpolymeric particle may be inorganic or organic compounds. In aparticular embodiment, the solid polymeric particles of the presentdisclosure may consist essentially of a fluoropolymer including onlyunavoidable impurities.

The amount of the solid particles contained in the mixture can be in arange that a percolated network be formed, and that the createdthree-dimensional body can be densified without falling apart uponburnout of the binder. In one embodiment, the amount of the solidparticles can be at least 10 vol %, such as at least 15 vol %, at least20 vol %, at least 25 vol %, or at least 30 vol % based on the totalvolume of the mixture. In another embodiment, the particle content canbe not greater than 70 vol %, such as not greater than 65 vol %, notgreater than 60 vol %, not greater than 55 vol %, or not greater than 50vol %. It will be appreciated that the amount of solid particles can bea value between any of the maximum and minimum values noted above, suchas from 10 vol % to 70 vol %, from 15 vol % to 60 vol %, or from 20 vol% to 45 vol % based on the total volume of the mixture.

In a certain embodiment, the mixture can be prepared by using asstarting material a dispersion of the solid particles. In one aspect,the dispersion may include solid polymeric particles, a solvent, and asurfactant. The solid polymeric particles may not dissolved in thesolvent of the dispersion and maintain solid. Suitable solvents of thedispersion can be water, ethanol, acetone, dimethyl sulphoxide (DMSO),dimethylformamide (DMF), tetrahydrofuran (THF), methyl-ethylketone,ethyl acetate, methylene chloride, N-methyl-2-pyrrolidone (NMP), afluor-solvent, or any combination thereof.

In one embodiment, the solvent can be a component of the mixtureexceeding the amount of the binder and/or the solid particles. Inaspects, an amount of the solvent can be at least 10 wt % based on atotal weight of the mixture, such as at least 15 wt %, at least 20 wt %,at least 25 wt %, at least 30 wt %, or at least 35 wt %. In anotheraspect, the amount of the solvent can be not greater than 65 wt % basedon a total weight of the mixture, such as not greater than 60 wt %, notgreater than 55 wt %, not greater than 50 wt %, not greater than 45 wt%, or not greater than 40 wt %. The amount of solvent in the mixture canbe a value between any of the maximum and minimum numbers noted above,such as from 10 wt % to 65 wt %, from 15 wt % to 55 wt %, or from 20 wt% to 50 wt %.

In a certain embodiment, it is desirable that the curable binder is atleast partially soluble in the solvent contained in the mixture. Thecurable binder of the mixture of the present disclosure can comprisepolymerizable monomers and/or polymerizable oligomers. Non-limitingexamples of polymerizable monomers and oligomers can be: an acrylate, anacrylamide, an urethane, a diene, a sorbate, a sorbide, a carboxylicacid ester, or any combination thereof. In a particular embodiment, thecurable binder can include a water-soluble difunctional acrylic monomer.In another particular embodiment, the curable binder can be acombination of a water-soluble difunctional acrylic monomer and awater-insoluble polyester acrylate oligomer. Further examples ofacrylate binder can be 1,4,-butanediol diacrylate or 1,6-hexanedioldiacrylate.

In an embodiment, an amount of the curable binder can be at least 1 wt %based on a total weight of the mixture, such as at least 2 wt %, atleast 3 wt %, or at least 5 wt %. In other embodiments, the binder maybe present in an amount not greater than 25 wt % based on a total weightof the mixture, such as not greater than 20 wt %, not greater than 18 wt%, not greater than than 15 wt %, not greater than 10 wt %, or notgreater than 8 wt %. The amount of the curable binder in the mixture canbe a value between any of the maximum and minimum values noted above,such as from 1 wt % to 25 wt %, from 5 wt % to 20 wt %, or from 10 wt %to 17 wt % based on a total weight of the mixture.

In order to keep the solid particles well dispersed in the mixture, oneor more surfactants can be added to the mixture. If a dispersion ofsolid particles is used as starting material, the surfactant containedin the dispersion may be sufficient to keep the solid particlesdispersed in the final mixture. The surfactant can be a non-ionicsurfactant, an anionic surfactant, a cationic surfactant, or anycombination thereof. In certain embodiments, the surfactant can be afatty acid ester, a fluorosurfactant, or a combination thereof.

In one embodiment, the surfactant contained in the mixture can bepresent in an amount of at least 0.05 wt %, such as at least 0.1 wt %,at least 0.5 wt %, at least 1 wt % or at least 2 wt % based on the totalweight of the of the mixture. In another embodiment, the amount ofsurfactant may be not greater than 15 wt %, such as not greater than 10wt %, not greater than 7 wt %, or not greater than 5 wt % based on atotal weight of the mixture. The amount of surfactant can be a valuebetween any of the maximum and minimum values noted above, such as from0.05 wt % to 15 wt %, from 0.5 wt % to 10 wt % or from, or from 1 wt %to 5 wt %.

The mixture can further include a photoinitiator. The photoinitiator canbe a free-radical photoinitiator. In a particular aspect, a free-radicalphotoinitiator can be employed, which can be inhibited by the presenceof oxygen. Non-limiting examples of free-radical photoinitiators caninclude ketones or phosphine oxides, such as IRGACURE™ 819(bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide), ESSTECH TPO(2,4,6-trimethylbenzoyl)-phenylphosphineoxide) or a combination thereof.

In an embodiment where a cationic photoinitiator is used, thephotopolymerization generally tends to be slower and cannot be inhibitedby oxygen. In this aspect, instead of oxygen as inhibitor, a Bronstedacid or Lewis acid, such as metal halides and their organometallicderivatives can be employed and released from the bottom window of thepolymerization chamber to form an inhibition zone.

According to another embodiment of the present disclosure, the mixturemay further include a dye. The dye can function as an additionalinhibitor by absorbing excess radiation energy and may improve theresolution of the formed three-dimensional body. In one embodiment, thedye can be a fluorescent dye. The fluorescent dye can be selected fromthe classes of rhodamine dyes, fluorine dyes, acridine dyes, cyaninedyes, phenanthrine dyes, or acridine dyes. In one aspect, the dye can bea rhodamine, for example, Rhodamine B, Rhodamine 6G, Rhodamine 123, or arhodamine derivative, e.g., Rhodamine B isothiocyanate. In a particularaspect, the dye may be Rhodamine B. In another aspect, the dye can be afluorone dye, for example Fluorescein. Other suitable examples of dyes,but not limited thereto, can be IR-780 perchlorate(1,1′,3,3,3′,3′-4,4′,5,5′-di-benzo-2,2′-indotricarbocyanineperchlorate), Crystal Violet, or a combination thereof.

The suitability of a dye with regard to the resolution and the strengthof the formed body can vary largely. For example, it has been observedthat Rhodamine B can be advantageous for improving the resolution of aprinted body with no detrimental influence on the strength of the body,while Fluorescin may improve the resolution of a formed body undercertain conditions but can be of disadvantage regarding a desiredstrength of the body.

The amount of dye in the mixture for forming a three dimensional bodyhaving an improved resolution of the formed body in comparison to notusing a dye can depend on several factors, for example, the amount ofsolid polymeric particles in the mixture, the thickness of theinhibition zone, the radiation intensity during forming, the formingspeed, the amount of photoinitiator, or a combination thereof. In oneembodiment the dye may be present in an amount of at least 0.01 wt %based on the total weight of the mixture, such as at least 0.025 wt %,or at least 0.03 wt %, or at least 0.05 wt %, or at least 0.075 wt %based on the total weight of the mixture. In another embodiment, theamount of dye in the mixture may be not greater than 1 wt %, such as notgreater than 0.5 wt %, or not greater than 0.2 wt %, or not greater than0.1 wt %. The amount of dye in the mixture can be a value between any ofthe maximum and minimum values noted above, such as from 0.01 wt % to 1wt %, from 0.03 wt % to 0.5 wt %, or from 0.05 wt % to 0.1 wt % based onthe total weight of the dye. In a particular embodiment, the dye can beRhodamine B in an amount of at least 0.01 wt % to not greater than 0.2wt %.

The mixture of the present disclosure can further include one or moreadditives. Non-limiting examples of additives can be plasticizers,dispersing agents, debinding accelerators, cross-linking monomers, pHregulators, a pharmaceutically active ingredient, a defoamer, aprocessing aid, or any combination thereof.

The rheological properties of the mixture containing solid particles anda radiation curable material may be controlled to facilitate suitableformation of a stable and suitably formed three-dimensional body,including for example, a polymeric three-dimensional body havingsufficient strength to be self-supporting and capable of handlingwithout detrimental deformation. Also, the force required tocontinuously pull-up the carrier the force utilized to pull the carrierplate away from the chamber may be adjusted based on various parameters,including but not limited to the rheology of the mixture.

In a further aspect, the mixture may have a low shear viscosity toprevent particle settling over the duration of the forming of thethree-dimensional body. Furthermore, the solid polymeric particlescontained in the slurry may be uniformly dispersed throughout theradiation curable material when electromagnetic radiation is conductedsuch that that the three-dimensional body can shrink uniformly duringsintering. Non-uniform distribution of the solid polymeric particles mayresult in forming of undesirable macro-structural or micro-structuralfeatures, including for example, undesirable porosity and the like.Under low shear rate may be understood a range of not greater about 5 Hzand at least about 0.1 Hz, with a corresponding viscosities from atleast about 50 cP to not greater than about 100000 cP.

In one embodiment, the mixture may be formed such that the content ofagglomerates of the solid particles is limited. In a certain embodiment,the mixture can be essentially free of agglomerates of solid polymericparticles.

In one aspect, the yield point of the mixture may be less than 10 Pa,such as less than 8 Pa, less than 5 Pa, or less than 3 Pa at roomtemperature.

After forming of the three-dimensional body, the body can be subjectedto drying for removing the solvent from the formed body. Drying can beconducted at an elevated temperature and/or under applied vacuum. In oneembodiment, the drying temperature can be close to the boilingtemperature of the solvent being removed from the body, but should notexceed the boiling point of the solvent by more than 20° C. In a certainaspect, the solvent contained in the three-dimensional body can bewater, and the body can be dried at a temperature not greater than 120°C., such as not greater than 115° C., not greater than 110° C., or notgreater than 105° C.

In one embodiment, the three-dimensional body may shrink during drying.The shrinkage of the three-dimensional body after drying, based on thesize of the body before drying, can be at least 1%, such as at least 3%,at least 5%, or at least 7%. In another embodiment, the shrinkage afterdrying can be not greater than 30%, such as not greater than 25%, notgreater than 20%, not greater than 15%, or not greater than 10%, basedon the total size of the body before drying. The shrinkage can be avalue between any of the minimum and maximum values note above, such asfrom 1% to 30%, from 5% to 20%, or from 10% to 15%. As used herein, theshrinkage in any of the three dimensions (x, y, z) is calculatedaccording to equation

${s = {{\ln\left( \frac{l_{f}}{l_{0}} \right)}}},$where l₀ and l_(f) are respectively the initial and final dimensions ofthe object measured with a caliper.

After drying, the three-dimensional body can be subjected to furtherheating to remove the cured binder by decomposition to volatilecompounds. In a certain embodiment, the decomposition temperature of thebinder can be at least 150° C., such as at least 180° C., at least 190°C., or at least 200° C. In another embodiment, the temperature fordecomposing the binder may be not greater than 300° C., such as notgreater than 280° C., or not greater than 250° C. The temperature fordecomposing the binder can be a value between any of the minimum andmaximum values noted above, such as from 150° C. to 300° C., from 190°C. to 270° C., or from 200° C. to 280° C.

In one embodiment, the cured binder can be decomposed during heattreatment such that a weight loss of the binder in the body can be atleast 10 wt % based on the total weight of the cured binder, such as atleast 20 wt %, at least 30 wt %, at least 40 wt %, at least 50 wt %, atleast 70 wt %, at least 80 wt %, at least 90 wt %, at least 95 wt %, atleast 98 wt %, at least 99 wt %, or at least 99.95 wt %.

In one aspect, the temperature during the binder removal can beincreased above a decomposition temperature of the binder, but below thethermal transition temperature of the solid polymeric particlescontained in the body. In another aspect, complete binder removal may beobtained above the sintering temperature.

Following the removal or partial removal of the cured binder, thethree-dimensional body can be subjected to high temperature sintering.During high temperature sintering, the solid polymeric particles of thebody can coalesce to form a more densified body by lowering the surfaceenergy.

In one embodiment, the sintering temperature may be not less than 60° C.below a thermal transition temperature of the solid particles, such asnot less than 50° C., not less than 30° C., not less than 20° C., notless than 15° C., not less than 10° C., or not less than 5° C.

In another embodiment, the sintering temperature can be not less than 5°C. below the decomposition temperature of the solid polymeric particles,such as not less than 10° C., not less than 15° C., not less than 20°C., not less than 50° C., or not less than 100° C. below thedecomposition temperature of the solid particles.

After high temperature sintering, the bulk density of the sinteredthree-dimensional body can be at least 0.2 g/cm³, such as at least 0.5g/cm³, at least 1.0 g·cm³, at least 1.5 g/cm³, at least 1.8 g/cm³, atleast 1.9 g/cm³, at least 2.0 g/cm³, at least 2.05 g·cm³, or at least2.1 g/cm³.

In further embodiments, the sintered three-dimensional body can have acrystallinity of at least 10%, such as at least 13%, at least 20%, or atleast 30%.

The formed fluoropolymeric bodies of the present disclosure can havedesired strength properties. In one embodiment, a formed fluoropolymericbody after high temperature sintering can have a tensile strength atmaximum load of at least 5 MPa, such as at least 10 MPa, at least 12MPa, at least 14 MPa, at least 16 MPa, or at least 18 MPa, or at least20 MPa. In another aspect, the tensile strength at maximum load may benot greater than not greater than 35 MPa, such as not greater than 30MPa, not greater than 25 MPa, or not greater than 22 MPa. The tensilestress at maximum load may be a value between any of the minimum andmaximum values noted above.

The sintered three-dimensional body of the method of the presentdisclosure can further have an elongation of break at a temperature of25° C. of at least 50%, such as at least 70%, at least 90%, at least100%, at least 110%, at least 150%, such as at least 160%, at least170%, at least 180%, at least 190%, or at least 200%. In anotherembodiment, the elongation of break can be not greater than 1000%, suchas not greater than 800%, not greater than 600%, not greater than 400%,not greater than 350%, not greater than 330%, or not greater than 300%.The elongation of break at a temperature of 25° C. can be a valuebetween any of the minimum and maximum values note above.

In a further embodiment, the sintered three-dimensional body can have arelative density of at least 40%, such as at least 50%, at least 60%, orat least 70%, at least 80%, at least 90%, or at least 95% with respectto a fluoropolymeric material having a density of 2.2 g/cm³.

The process of the present invention can form sintered three-dimensionalpolymeric bodies from solid polymeric particles which are already fullypolymerized in the uncured mixture and possess a high meltingtemperature, wherein the melting temperature is higher than thedecomposition temperature of the cured binder. Especially suitablepolymeric particles can be fluoropolymer particles because of their highmelting temperature.

In a particular embodiment, the sintered three-dimensional body canconsist essentially of PTFE particles. As used herein, consistingessentially of PTFE particles is intended to mean that the sintered bodyincludes at least 90 wt % PTFE, such as at least 95 wt %, or at least 99wt % based on the total weight of the sintered body. The process of thepresent disclosure allows a unique way of producing complexthree-dimensional PTFE bodies which cannot be made by other knowntechniques or require much higher production efforts. It is known thatPTFE, unlike other thermoplastics, is not melt-flow processable, whichmeans it does not flow when heated above its melting point. Accordingly,PTFE cannot be injection molded, which makes it very difficult toproduce complex conventional shapes with PTFE that can be easilyproduced with other polymers.

The method of the present disclosure can form three dimensional bodiescomprising fluoropolymeric particles, which may have after sintering ahigh size resolution. In one embodiment, the size resolution of thesintered body can be not greater than 300 microns, such as not greaterthan 280 microns, not greater than 260 microns, not greater than 240microns, not greater than 220 microns, not greater than 200 microns, ornot greater than 190 microns. As used herein, the term size resolutionmeans that the process is capable of forming a three-dimensional bodyhaving an isolated body feature of a height of 1 mm and a thickness ofnot greater than 300 microns, such as not greater than 280 microns, notgreater than 260 microns, not greater than 240 microns, not greater than220 microns, not greater than 200 microns, or at not greater than 190microns.

As further demonstrated in the Examples below, the method of the presentdisclosure can produce complex three-dimensional fluoropolymeric bodieswith a high resolution in a continuous and fast forming process. Thesolid polymeric particles can be pre-selected in form of commerciallyavailable solid particle dispersions and integrated in a mixturecomprising a curable binder.

Many different aspects and embodiments are possible. Some of thoseaspects and embodiments are described herein. After reading thisspecification, skilled artisans will appreciate that those aspects andembodiments are only illustrative and do not limit the scope of thepresent invention. Embodiments may be in accordance with any one or moreof the embodiments as listed below.

Embodiment 1

A method of forming a three-dimensional body, comprising: providing amixture comprising a curable binder and dispersed solid polymericparticles; and forming a three-dimensional body from the mixture bycuring the binder to form a cured binder, wherein forming includestranslation and growth of the three-dimensional body from an interfaceof the mixture, and the solid polymeric particles have a higher thermaltransition temperature than a decomposition temperature of the curedbinder.

Embodiment 2

A method of forming a three-dimensional body, comprising: providing amixture comprising a curable binder and dispersed solid particles, thesolid particles including a fluoropolymer; and forming athree-dimensional body from the mixture by curing the binder to form acured binder, wherein forming includes translation and growth of thethree-dimensional body from an interface of the mixture.

Embodiment 3

The method of Embodiments 1 or 2, wherein preparing the mixture includescombining a dispersion of the solid polymeric particles with the curablebinder, wherein the dispersion includes a solvent, and at least aportion of the curable binder is soluble in the solvent.

Embodiment 4

The method of Embodiment 3, wherein the solvent is water.

Embodiment 5

The method of any of the preceding Embodiments, further comprisingremoving at least a portion of the cured binder from the formedthree-dimensional body by a chemical treatment or a thermal treatment;followed by sintering to obtain a sintered three-dimensional body.

Embodiment 6

The method of Embodiment 5, wherein sintering is conducted at asintering temperature not less than 60° C. below the thermal transitiontemperature of the solid particles, such as not less than 50° C., notless than 30° C., not less than 20° C., not less than 15° C., not lessthan 10° C., or not less than 5° C.

Embodiment 7

The method of Embodiment 5, wherein sintering is conducted at asintering temperature not less than 5° C. below a decompositiontemperature of the solid particles, such as not less than 10° C., notless than 15° C., or not less than 20° C.

Embodiment 8

The method of any of the preceding Embodiments, wherein the mixturefurther comprises a surfactant.

Embodiment 9

The method of Embodiment 8, wherein the surfactant includes a non-ionicsurfactant, an anionic surfactant, a cationic surfactant, or anycombination thereof.

Embodiment 10

The method of Embodiment 9, wherein the surfactant includes a fatty acidester, a fluorosurfactant, or any combination thereof.

Embodiment 11

The method of any of the preceding Embodiments, wherein the mixturefurther includes a dye.

Embodiment 12

The method of Embodiment 11, wherein the dye comprises a fluorescentdye.

Embodiment 13

The method of Embodiment 12, wherein the fluorescent dye is selectedfrom a rhodamine dye, a fluorone dye, a cyanine dye, an acridine dye, acyanine dye, a phenanthridine dye, an oxazine dye, or any combinationthereof.

Embodiment 14

The method of Embodiments 12 or 13, wherein the fluorescent dyecomprises a rhodamine dye.

Embodiment 15

The method of Embodiments 13 or 14, wherein the rhodamine dye includesRhodamine B.

Embodiment 16

The method of any of Embodiments 11 to 15, wherein an amount of the dyeis at least 0.01 wt %, such as at least 0.025 wt %, or at least 0.05 wt% based on the total weight of the mixture.

Embodiment 17

The method of any of Embodiments 11 to 16, wherein an amount of the dyeis not greater than 1 wt %, such as not greater than 0.5 wt %, notgreater than 0.2 wt %, not greater than 0.15 wt %. or not greater than0.1 wt % based on a total weight of the mixture.

Embodiment 18

The method of Embodiment 15, wherein the Rhodamine B is present in anamount of at least 0.01 wt % to not greater than 0.2 wt % based on atotal weight of the mixture.

Embodiment 19

The method of any of the preceding Embodiments, wherein the mixturecomprises at least 10 vol % of the solid particles based on a totalvolume of the mixture, such as at least 15 vol %, at least 20 vol %, atleast 25 vol %, or at least 30 vol % based on a total volume of themixture.

Embodiment 20

The method of any of the preceding Embodiments, wherein the mixturecomprises not greater than 70 vol % of the solid particles based on atotal volume of the mixture, such as not greater than 65 vol %, notgreater than 60 vol %, not greater than 55 vol %, or not greater than 50vol % based on a total volume of the mixture.

Embodiment 21

The method of any of the preceding Embodiments, wherein the solidparticles have an average primary particle size of at least 60 nm, suchas at least 70 nm, at least 80 nm, at least 100 nm, at least 150 nm, atleast 200 nm, at least 230 nm, or at least 260 nm.

Embodiment 22

The method of any of the preceding Embodiments, wherein the solidparticles have an average primary particle size not greater than 10microns, such as not greater than 8 microns, not greater than 5 microns,or not greater than 1 micron.

Embodiment 23

The method of any of the preceding Embodiments, wherein the mixtureincludes solid polymeric particle aggregates formed from the solidpolymeric particles, wherein a average particles size of the solidpolymeric particle aggregates is not greater than 50 microns, such asnot greater than 35 microns, not greater than 20 microns, or not greaterthan 15 microns.

Embodiment 24

The method of any of the preceding Embodiments, wherein the solidparticles include polytetrafluoroethylene (PTFE),tetrafluoroethylene-hexafluoropropylene (FEP), perfluoroalkoxyethylene(PFA), ethylene-tetrafluoroethylene (ETFE), polyvinylidone fluoride(PVDF), ethylene-chlorotrifluoroethylene (ECTFE), perfluoromethyl vinylether (MFA), or any combination thereof.

Embodiment 25

The method of Embodiment 24, wherein the solid particles consistessentially of PTFE.

Embodiment 26

The method of any of the preceding Embodiments, wherein the thermaltransition temperature of the solid polymeric particles is at least 300°C., such as at least 310° C., or at least 320° C.

Embodiment 27

The method of any of the preceding Embodiments, wherein the thermaltransition temperature of the solid polymeric particles is not greaterthan 360° C., such as not greater than 340° C., or not greater than 330°C.

Embodiment 28

The method of any of the preceding Embodiments, wherein the solidparticles have molecular weight of at least 1×10⁵ g/mol, such as atleast 5×10⁵ g/mol, at least 1×10⁶ g/mol, at least 5×10⁶ g/mol, or atleast 1×10⁷ g/mol.

Embodiment 29

The method of any of the preceding Embodiments, wherein the solidparticles have a molecular weight not greater than 9×10⁷ g/mol, such asnot greater than 6×10⁷ g/mol, or not greater than 3×10⁷ g/mol.

Embodiment 30

The method of any of the preceding Embodiments, wherein the solidparticles have a crystallinity of at least 65%, such as at least 70%, atleast 80%, or at least 90%.

Embodiment 31

The method of any of Embodiments 3 to 30, wherein an amount of thesolvent in the mixture is at least 10 wt % based on a total weight ofthe mixture, such as at least 15 wt %, at least 20 wt %, at least 25 wt%, at least 30 wt %, or at least 35 wt %.

Embodiment 32

The method of any of Embodiments 3 to 31, wherein an amount of thesolvent in the mixture is not greater than 65 wt % based on a totalweight of the mixture, such as not greater than 60 wt %, not greaterthan 55 wt %, not greater than 50 wt %, not greater than 45 wt %, or notgreater than 40 wt %.

Embodiment 33

The method of any of the preceding Embodiments, wherein the curablebinder includes polymerizable monomers or polymerizable oligomers, thepolymerizable monomers or polymerizable oligomers including an acrylate,an acrylamide, a urethane, a diene, a sorbate, a sorbide, a carboxylicacid esters, or any combination thereof.

Embodiment 34

The method of Embodiment 33, wherein the curable binder includes adifunctional acrylic monomer and a polyester acrylate oligomer.

Embodiment 35

The method of any of the preceding Embodiments, wherein an amount of thecurable binder in the mixture is at least 1 wt % based on a total weightof the mixture, such as at least 2 wt %, at least 3 wt %, or at least 5wt %.

Embodiment 36

The method of any of the preceding Embodiments, wherein an amount of thecurable binder in the mixture is not greater than 20 wt % based on atotal weight of the mixture, such as not greater than 15 wt %, notgreater than 10 wt %, or not greater than 8 wt %.

Embodiment 37

The method of any of the preceding Embodiments, wherein the mixturefurther comprises a photoinitiator.

Embodiment 38

The method of Embodiment 37, wherein the photoinitiator is afree-radical photoinitiator.

Embodiment 39

The method of Embodiment 38, wherein the photoinitiator includes aperoxide, a ketone, a phosphine oxide, or any combination thereof.

Embodiment 40

The method of any of the preceding Embodiments, wherein forming isconducted at a forming speed of at least 1 mm/hour, such as at least 5mm/hour, at least 10 mm/hour, at least 20 mm/hour, at least 25 mm/hour,at least 40 mm/hour, at least 50 mm/hour, or at least 60 mm/hour.

Embodiment 41

The method of any of the preceding Embodiments, wherein forming isconducted at a forming speed of not greater than 5000 mm/hour, such asnot greater than 3000 mm/hour, not greater than 1000 mm/hour, notgreater than 500 mm/hour, or not greater than 100 mm/hour.

Embodiment 42

The method of any of the preceding Embodiments, wherein curing includesradiating using an electromagnetic radiation within a wavelength rangefrom at least 370 nm to not greater than 450 nm.

Embodiment 43

The method of Embodiment 42, wherein the electromagnetic radiation hasan energy within a range from at least 5 mJ/cm² to not greater than 450mJ/cm².

Embodiment 44

The method of any of the preceding Embodiments, wherein curing includesapplying electromagnetic radiation to the mixture having an energy of atleast 1 mJ/cm², such as at least 10 mJ/cm², at least 20 mJ/cm², at least30 mJ/cm², at least 50 mJ/cm² or at least 80 mJ/cm².

Embodiment 45

The method of any of the preceding Embodiments, wherein curing includesapplying electromagnetic radiation to the mixture having an energy notgreater than 450 mJ/cm², such as not greater than 400 mJ/cm², notgreater than 350 mJ/cm², not greater than 300 mJ/cm², not greater than250 mJ/cm², not greater than 200 mJ/cm², or not greater than 100 mJ/cm².

Embodiment 46

The method of any of the preceding Embodiments, wherein curing includesapplying electromagnetic radiation to the mixture having a power of atleast 0.1 mW/cm², such as at least 0.5 mW/cm², at least 1.0 mW/cm², atleast 2 mW/cm², or at least 3 mW/cm².

Embodiment 47

The method of any of the preceding Embodiments, wherein curing includesapplying electromagnetic radiation to the mixture having a power notgreater than 250 mW/cm², such as not greater than 100 mW/cm², notgreater than 50 mW/cm², or not greater than 10 mW/cm².

Embodiment 48

The method of any of the preceding Embodiments, wherein the mixture hasa viscosity at 25° C. of at least at least 10000 cP at a shear rate ofless than about 5 Hz, and a viscosity of less than 50 cP at a shear rategreater than about 25 Hz.

Embodiment 49

The method of any of Embodiments 5 to 48, wherein the sinteredthree-dimensional body has a crystallinity of at least 10%, such as atleast 13%, at least 20%, or at least 30%.

Embodiment 50

The method of any of Embodiments 5 to 48, wherein the sinteredthree-dimensional body has a bulk density of at least 0.2 g/cm3, such asat least 0.5 g/cm³, at least 1.0 g·cm3, at least 1.5 g/cm³, at least 1.8g/cm³, at least 1.9 g/cm³, at least 2.0 g/cm³, at least 2.05 g·cm³, orat least 2.1 g/cm³.

Embodiment 51

The method of any of Embodiments 5 to 50, wherein the sinteredthree-dimensional body has a tensile strength at maximum load of atleast 5 MPa, such as at least 10 MPa, at least 12 MPa, at least 14 MPa,at least 16 MPa, or at least 18 MPa.

Embodiment 52

The method of any of Embodiments 5 to 51, wherein the sinteredthree-dimensional body has a tensile strength at maximum load of notgreater than 35 MPa, such as not greater than 30 MPa, not greater than25 MPa, or not greater than 22 MPa.

Embodiment 53

The method of any of Embodiments 5 to 52, wherein the sinteredthree-dimensional body has an elongation of break of at least 50% at atemperature of 25° C., such as at least 70%, at least 90%, at least100%, at least 110%, at least 150%, such as at least 160%, at least170%, at least 180%, at least 190%, or at least 200%.

Embodiment 54

The method of any of Embodiments 5 to 53, wherein the sinteredthree-dimensional body has an elongation of break of not greater than1000% at a temperature of 25° C., such as not greater than 800%, notgreater than 600%, not greater than 400%, not greater than 350%, notgreater than 330%, or not greater than 300%.

Embodiment 55

The method of any of Embodiments 5 to 54, wherein the sinteredthree-dimensional body has a relative density of at least 40%, such asat least 50%, at least 60%, at least 70%, at least 80%, at least 90%, orat least 95% with respect to a fluoropolymeric material having a densityof 2.2 g/cm³.

Embodiment 56

The method of any of the preceding Embodiments, wherein forming of thebody is conducted continuously.

Embodiment 57

The method of any of the preceding Embodiments, wherein the formedthree-dimensional body has a size resolution of not greater than 300microns, such as not greater than 280 microns, not greater than 260microns, not greater than 240 microns, not greater than 220 microns, notgreater than 200 microns, or not greater than 190 microns.

Embodiment 58

The method of Embodiment 57, wherein the size resolution is not greaterthan 220 microns.

EXAMPLES

The following non-limiting examples illustrate the present invention.

Example 1

Preparing a Curable Mixture Comprising PTFE Particles.

A mixture was prepared by combining 76.6 vol % of an aqueous PTFEdispersion (DAIKIN D-610C from Daikin) with two water solublebinders: 1) 18.4 vol % of an acrylic-difunctional polyethylene glycol(SR344 from Sartomer, Arkema), and 2) 4.6 vol % of a polyester acrylateoligomer (CN2302 from Sartomer, Arkema) and 0.4 vol % of photo-initiatorIRGACURE 819 from BASF. The DAIKIN D610C PTFE dispersion contained 30vol % PTFE particles having an average particle size of 200 nm and 70vol % of a liquid including water and surfactant. The amount ofsurfactant in the DAIKIN dispersion was 6 wt % based on the amount ofsolid PTFE particles. A summary of the components of the mixture basedon total weight and volume of the mixture is also shown in Table 1 Themixture had a viscosity at a temperature of 25° C. and at a shear ratein a range of 0.1 s⁻¹ to 100 s⁻¹ between about 50000 to 100 cP (see FIG.3).

Example 2

Continuous Forming of a Three-Dimensional Body Comprising PTFEParticles.

The mixture prepared in Example 1 was placed in a chamber of an assemblyhaving a similar design as shown in FIG. 2A and FIG. 2B. Aselectromagnetic radiation unit was an array of LEDs having a UVwavelength maximum at 405 nm.

A series of flower-bud shaped bodies were formed by varying fromexperiment to experiment the forming speed (between 1 mm/min and 15mm/min) and an radiation intensity of 5 mW/cm². Best results could beobtained at a forming speed of 10 mm/min and a radiation intensity of 5mW/cm².

The formed flower-bud body was dried (removing of the water) at roomtemperature in an open lab environment for about 12 hours to a stableweight. The body had a weight loss of 28 wt % corresponding to the waterevaporation. During drying, the flower-bud body has shrinked by about15%.

After drying, the body was subjected to a further heat-treatment regimeto remove the cured binder and to conduct high temperature sintering.The temperature was increased at a speed of 1° C./min up to a maximumsintering temperature of 380° C. The temperature was maintained for 30minutes at 380° C., followed by free cooling (uncontrolled free coolingspeed of the oven, about 5-10° C./min). After sintering, the shrinkageof the body was about 32% based on the size of the formed bodies beforedrying and sintering, but the shape of the body was maintained, see alsoFIG. 4. The weight loss after sintering was 23 wt % based on the totalweight of the body after drying, which corresponds to the binder contentof about 20 wt % and about 3 wt % leftover water in the dried body.

The material of the sintered PTFE bodies had a density between 2 g/cm³and 2.1 g/cm³, measured by the Archimedes method, which corresponds to arelative density of 90%-95%, assuming a density of 2.2 g/cm³ for densenon-porous PTFE.

Example 3

Forming of Three-Dimensional Bodies Comprising PTFE Particles in thePresence of a Dye.

A mixture including solid PTFE particles was prepared similar as inExample 1, except that a dye was further added (Rhodamine B) in anamount of 0.05 wt % based on the total weight of the mixture, and onlyone type of binder (SR 344) was used in an amount of 22.8 vol % based onthe total volume of the mixture. The exact composition (S2) can be seenin Tables 1A and 1B below.

Different types of three dimensional bodies were formed from the mixtureS2 according to the printing conditions described in Example 2.

The formed bodies showed an improved resolution compared to the threedimensional bodies of Example 2 (S1), and a variety of shapes afterdrying and before sintering can be seen in FIGS. 5A, 5B, and 5C.

The bodies were subjected to drying and sintering according to thefollowing heat-treatment regime: 1° C./min up to 120° C.; 2° C./min upto 380° C.; 5 min isothermal heating at 380° C.; and cooling to roomtemperature at 10° C./min.

FIG. 6 shows a comparison of a PTFE comprising body printed from mixtureS2. The left image shows the body directly after forming and the rightimage after drying and sintering. The shrinkage rate after sintering wasabout 30% (in comparison to the size before drying); the sintered PTFEbody had a density of 2.0 g/cm3, and a relative density of about 90%.

Example 4

Forming of Three-Dimensional Bodies Comprising PFA or FEP Particles.

A mixture was prepared containing an aqueous dispersion of 200 nm sizedPFA particles (Teflon PFAD 335D from Chemours) mixed with water-solublebinder (SR344), a photoinitiator (IRGACURE 819), and a dye (Rhodamine Bfrom Sigma Aldrich). A similar mixture was prepared using an aqueousdispersion of solid FEP particles with an average size of 180 nm (TeflonFEPD 121 from Chemours) instead of the PFA dispersion; the amount of theother ingredients of the mixture was the same. The amounts of eachingredient based on a total amount of the mixtures are shown in Tables1A and 1B (samples S3 and S4).

TABLE 1A Type of solid Polymeric Photo- polymeric particles WaterSurfactant Binder Dye initiator Sample particles [vol %] [vol %] [vol %][vol %] [vol %] [vol %] S1 PTFE 31.11 42.89 2.74 22.81 0 0.46 S2 PTFE31.09 42.86 2.74 22.80 0.07 0.46 S3 FEP 27.64 47.01 2.74 22.11 0.07 0.44S4 PFA 31.09 42.86 2.74 22.8 0.07 0.46

TABLE 1B Type of solid Polymeric Photo- polymeric particles WaterSurfactant Binder Dye initiator Sample particles [wt. %] [wt. %] [wt. %][wt. %] [wt. %] [wt. %] S1 PTFE 49.83 31.23 1.99 16.61 0.00 0.33 S2 PTFE49.81 31.21 1.99 16.60 0.05 0.33 S3 FEP 45.66 35.30 2.05 16.60 0.05 0.33S4 PFA 49.81 31.21 1.99 16.60 0.05 0.33

From the prepared mixtures, three-dimensional bodies were formedaccording to the method described in Example 2 at a forming speed of 1mm/min and an applied radiation intensity of 10 mW/cm². It could beobserved that the presence of the dye showed a large improvement of theresolution of the formed bodies. FIGS. 7A and 7B illustrate athree-dimensional body comprising FEP formed with mixture S3 afterdrying. The addition of 0.05 wt % Rhodamine B could cause a remarkableimprovement in the resolution of a honeycomb structured body (rightimage, FIG. 7B) in comparison to the body formed without the presence ofthe dye (left image, FIG. 7A). Bodies with very good resolution could bealso obtained with other complex body structures, such as a flower-budor a threaded screw.

The following heat-treatment regimes were applied for drying andsintering of the FEP comprising bodies:

A) 2° C./min up to 120° C.; 5° C./min up to a 380° C., isothermalheating for 30 min at 380° C., followed by cooling at a rate of 10°C./min to room temperature.

B) 2° C./min up to 120° C.; 5° C./min up to a 300° C., isothermalheating for 15 min at 300° C., followed by cooling at a rate of 10°C./min to room temperature.

After high temperature sintering according to the heat treatment regimeA) of up to 380° C., the bodies partially collapsed.

At a lower maximum sintering temperature of 300° C. (heat treatmentregime B), the sintered bodies maintained their shape, see FIGS. 8A, 8B,and 8C.

A thermogravimetric analysis (TGA) of a FEP comprising body after drying(i.e., Sample S3, after removal of the water) is illustrated in FIG. 9.It can be seen that after drying, only a very minor amount of water(<3%) stayed in the body. A noticeable decrease in weight started at atemperature of 200° C., which corresponds to the decomposition of thecured binder. A weight loss of about 5 wt % binder based on the totalamount of the binder was reached at a temperature of about 210° C.,which relates to the decomposition temperature of the binder inaccordance with the present disclosure. No remarkable differences in thespeed of the weight decrease could be observed until the melting pointof the FEP particles (260° C.) and the maximum sintering temperature(380° C.), which indicates that after sintering, a certain amount ofbinder was still present in the body. A first plateau was reached at atemperature of about 450° C., indicating that at this point, all binderwas removed. The following large drop in mass starting at about 525° C.appears to relate to the decomposition of the FEP particles. The densityof the material of the FEP-based body after sintering at 380° C. was2.19 g/cm³. The density was determined by the Archimedes method.

Example 5

Influence of Dye Concentration on Resolution of Printed PTFE Bodies

Mixtures were prepared including solid PTFE particles with varyingconcentration of Rhodamine B. The mixtures contained 76.6 vol % of anaqueous PTFE dispersion (DAIKIN D-610C from Daikin) having an averageparticle size of 200 nm, 22 vol % of an acrylic difunctionalpolyethylene glycol (SR344 from Sartomer, Arkema), 0.11 vol % of aphotoinitiator (IRGACURE 819 from BASF) and about 1.4 vol. % of adefoamer. The Rhodamine B concentration was varied at concentrations of0.025 wt %, 0.075 wt %, 0.1 wt %, and 0.2 wt % based on the total weightof the mixture.

A summary of the tested compositions is shown in Tables 2A and 2B. Allconcentrations are shown in vol % and wt % based on the total volume orweight of the mixtures.

TABLE 2A Amount of PTFE Photo- particles Water Surfactant BinderRhodamine initiator Defoamer Sample [wt %] [wt %] [wt %] [wt %] B [wt %][wt %] [wt %] S5 49.8 30.2 3.0 15.89 0.025 0.08 1.0 S6 49.8 30.2 3.015.84 0.075 0.08 1.0 S7 49.8 30.2 3.0 15.82 0.100 0.08 1.0 S8 49.8 30.23.0 15.72 0.200 0.08 1.0

TABLE 2B Amount of PTFE Photo- particles Water Surfactant BinderRhodamine initiator Defoamer Sample [vol %] [vol %] [vol %] [vol %] B[vol %] [vol %] [vol %] S5 31.1 41.5 4.1 21.82 0.034 0.11 1.374 S6 31.141.5 4.1 21.75 0.103 0.11 1.374 S7 31.1 41.5 4.1 21.72 0.137 0.11 1.374S8 31.1 41.5 4.1 21.58 0.275 0.11 1.374

From the mixtures listed in Table 2A/2B, defined three dimensionalbodies were continuously formed according to the method described inExample 2 at a forming speed of 0.5 mm/min and an applied radiationintensity of 4 mW/cm². Three-dimensional bodies were formed frommixtures S5-S7 (mixture S8 was not printable under the definedconditions). The form of the printed bodies was based on a specificallydesigned 3D model to investigate the minimum printable feature size independency to the amount of Rhodamine B in the mixture. The 3D modelcontained six parallel arranged walls of 1 mm height, with varying wallthickness: 50 microns, 100 microns, 150 microns, 300 microns, 450microns, and 600 microns. A magnified drawing of the 3D model is shownin FIGS. 11A and 11B.

The difference in the obtained resolution of the formed bodies afterdrying is illustrated in the comparison of FIGS. 12A; 12B, and 12C,which show images of formed three dimensional dried bodies printed frommixtures including 0.025 wt %, 0.075 wt %, and 0.1 wt % Rhodamine Brespectively. Drying was conducted at 40° C. until a stable weight wasobtained. It can be seen that at 0.025 wt % (FIG. 12A) and at 0.1 wt %(FIG. 12C) Rhodamine B, the resolution of the formed bodies was notsharp and each wall showed large irregularities and no clear gap betweenthe walls could be formed. At 0.075 wt % Rhodamine B concentration (FIG.12B), the printed three dimensional body included three of the six wallsof the 3D model, missing only the thinnest walls with a thickness of 50microns, 100 microns and 150 microns.

FIGS. 13A and 13B show top view images of the PTFE body shown as sideview in FIG. 12B, formed with 0.075 wt % Rhodamine B. It can be seenthat the walls do not connect with each other. In FIG. 13A, thethickness of each of the formed walls was measured at five differentlocations and compared with the wall thickness of the correspondingmodel. In FIG. 13B, the gap size between two adjacently formed walls atfive different positions was measured and an average value calculated. Asummary of the measured data is shown in Tables 3 and 4.

The thinnest isolated wall structure which could be formed had athickness of 246 microns±39 microns. The resolution data indicate thatby carefully selecting the concentration of Rhodamine B in the printingmixture, fine structure units having a size resolution of not greaterthan 250 microns can be formed in a dried body. As used herein, the termsize resolution of not greater than 250 microns relates to the printingof an isolated structure unit having a height of at least 1 mm and athickness of not greater than 250 microns after drying.

The average gap size (average value of measured gap size at fivedifferent positions and standard deviation) was 671 microns±27 micronsbetween the largest and medium thick walls, while the gap between themedium and smallest formed wall was 585 microns±60 microns.

While the distance (gap) between the walls is in good agreement with thepredicted drying shrinkage of 15%, the formed wall thicknesses werelower than what is estimated from a 15% shrinkage. This can be relatedto the fact fine features (like a thin wall) may require more UVexposure during printing than larger features to be fully formed. Thiseffect can be corrected by either adding more radiation intensity whenforming fine features or by over scaling in order to compensate andachieve a desired feature size.

TABLE 3 Model wall size assuming Wall Average 15% Average wall thicknesswall sizes drying sizes of dried variation in after Wall thickness Modelwall shrinkage green body dried green sintering variation after sizes[μm] [μm] [μm] body [±μm] [μm] sintering [±μm] 50 41 not formed 100 82not formed 150 123 not formed 300 246 246 39 190 22 450 368 300 7 244 9600 491 430 22 359 23

TABLE 4 Model: Gaps between walls Average Gap Average Gap assumingDistance variation Distance variation 15% between walls between wallsbetween between walls Model: Gaps drying in dried in dried walls afterafter between shrinkage green body green body sintering sintering walls[μm] [μm] [μm] [±μm] [μm] [±μm] 760 654 671 27 577 21 760 654 585 60 49625

The three dimensional body formed with a concentration of 0.075 wt %Rhodamine B was further subjected to high temperature sintering of thefollowing heat treatment regime: 1° C./min up to 120° C.; 2° C./min upto 380° C.; 5 min isothermal heating at 380° C.; and cooling to roomtemperature at 10° C./min.

Images of the three dimensional body after sintering are shown in FIGS.14A, 14B, 14C, and 14D. It can be seen that the three walls of the body(resolution lines) survived the sintering process. FIG. 14C illustratesthe positions of measuring the wall thickness after sintering. FIG. 14Dshows the positions of measuring the distance between the walls, whichare called herein also gaps.

The data demonstrate that it is possible by carefully selecting theconcentration of Rhodamine B in the printing mixture to form fine thinstructure units at a size resolution of not greater than 190 microns inthe sintered PTFE bodies.

Example 6

Mechanical Properties of Continuously Formed Sintered PTFE Bodies.

Rectangular PTFE rods were continuously formed from mixtures asdescribed in Example 5, using 0.05 wt % Rhodamine B and as PTFEdispersion Daikin 210C, containing PTFE particles with an averageparticle size of 220-250 nm. After continuous forming and drying thePTFE comprising bodies, the dried bodies were high temperature sinteredaccording to the temperature regime described in Example 3. Therectangular rods were tested in x-y direction for tensile strength atmaximal load and elongation at break according to modified ASTM 4894. Asused herein, modified ASTM 4894 means that the shape of the tested bodywas different. The rectangular shape of the sintered PTFE body to betested had a length of 18 mm, a width of 3.95 mm, and a thickness of1.46 mm. Each test was repeated six times and an average valuecalculated with error estimated as three times the standard deviationdivided by the square root of the numbers of tests. A summary of thetest results is shown in Table 5. An illustration of a tested PTFE bodybefore and after strain break is shown in FIG. 15.

TABLE 5 Property Average Value Tensile Strength at 18.8 ± 2.0 maximumload [MPa] Elongation at break [%] 188 ± 53

In the foregoing specification, the concepts have been described withreference to specific embodiments. However, one of ordinary skill in theart appreciates that various modifications and changes can be madewithout departing from the scope of the invention as set forth in theclaims below. Accordingly, the specification and figures are to beregarded in an illustrative rather than a restrictive sense, and allsuch modifications are intended to be included within the scope of theinvention.

What is claimed is:
 1. A method of forming a three-dimensional body,comprising: providing a liquid mixture comprising a curable binder anddispersed solid fluoropolymeric particles; and forming athree-dimensional body from the liquid mixture by curing the binder toform a cured binder, wherein forming includes translation and growth ofthe three-dimensional body from an interface of the liquid mixture. 2.The method of claim 1, wherein forming of the body is conductedcontinuously.
 3. The method of claim 1, further comprising removing atleast a portion of the cured binder from the formed three-dimensionalbody by a chemical treatment or a thermal treatment; followed bysintering to obtain a sintered three-dimensional body.
 4. The method ofclaim 3, wherein sintering is conducted at a sintering temperature notless than 50° C. below a thermal transition temperature of the solidfluoropolymeric particles.
 5. The method of claim 4, wherein sinteringis conducted at a sintering temperature not less than 10° C. below adecomposition temperature of the solid fluoropolymeric particles.
 6. Themethod of claim 3, wherein the sintered three-dimensional body has atensile strength at maximum load of at least 12 MPa.
 7. The method ofclaim 3, wherein the sintered three-dimensional body has an elongationof break of at least 100% at a temperature of 25° C.
 8. The method ofclaim 1, wherein the liquid mixture further includes a dye.
 9. Themethod of claim 8, wherein the dye is selected from a rhodamine dye, afluorone dye, a cyanine dye, an acridine dye, a cyanine dye, aphenanthridine dye, an oxazine dye, or any combination thereof.
 10. Themethod of claim 9, wherein the rhodamine dye includes Rhodamine B. 11.The method of claim 8, wherein an amount of the dye is at least 0.01 wt% and not greater than 0.5 wt % based on the total weight of the liquidmixture.
 12. The method of claim 8, wherein the dye is Rhodamine B andpresent in an amount of at least 0.02 wt % to not greater than 0.1 wt %based on a total weight of the liquid mixture.
 13. The method of claim1, wherein an amount of the solid fluoropolymeric particles in theliquid mixture is at least 15 vol % and not greater than 70 vol % basedon a total volume of the liquid mixture.
 14. The method of claim 1,wherein the solid fluoroploymeric particles have an average primaryparticle size of at least 80 nm.
 15. The method of claim 1, wherein thesolid fluoroploymeric particles include polytetrafluoroethylene (PTFE),tetrafluoroethylene-hexafluoropropylene (FEP), perfluoroalkoxyethylene(PFA), ethylene-tetrafluoroethylene (ETFE), polyvinylidone fluoride(PVDF), ethylene-chlorotrifluoroethylene (ECTFE), perfluoromethyl vinylether (MFA), or any combination thereof.
 16. The method of claim 15,wherein the solid fluoroploymeric particles consist essentially of PTFE.17. The method of claim 15, wherein the solid fluoroploymeric particlesinclude polytetrafluoroethylene (PTFE),tetrafluoroethylene-hexafluoropropylene (FEP), perfluoroalkoxyethylene(PFA), or any combination thereof.
 18. The method of claim 1, wherein anamount of the solvent in the liquid mixture is at least 10 wt % based ona total weight of the liquid mixture.
 19. The method of claim 1, whereinthe curable binder includes polymerizable monomers or polymerizableoligomers, the polymerizable monomers or polymerizable oligomersincluding an acrylate, an acrylamide, a urethane, a diene, a sorbate, asorbide, a carboxylic acid esters, or any combination thereof.
 20. Themethod of claim 1, wherein forming is conducted at a forming speed of atleast 10 mm/hour.
 21. The method of claim 1, wherein the fluoropolymericparticles do not dissolve in the liquid mixture.
 22. A method of forminga three-dimensional body, comprising: providing a liquid mixturecomprising a curable binder and dispersed solid polymeric particles; andforming a three-dimensional body from the liquid mixture by curing thebinder to form a cured binder, wherein forming includes translation andgrowth of the three-dimensional body from an interface of the liquidmixture, and the solid polymeric particles have a higher thermaltransition temperature than a decomposition temperature of the curedbinder.